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spi: davinci: do not use DMA if transfer length is less than 16 

Higher bitrate and lower CPU load if using PIO in this case.

Signed-off-by: Frode Isaksen <fisaksen@baylibre.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Frode Isaksen 2017-02-23 19:01:59 +01:00 committed by Mark Brown
parent 6b3a631e7f
commit 0718b76488
1 changed files with 8 additions and 6 deletions
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14
drivers/spi/spi-davinci.c
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@ -109,6 +109,8 @@
#define SPIDEF 0x4c
#define SPIFMT0 0x50
#define DMA_MIN_BYTES 16
/* SPI Controller driver's private data. */
struct davinci_spi {
struct spi_bitbang bitbang;
@ -479,7 +481,8 @@ static bool davinci_spi_can_dma(struct spi_master *master,
bool can_dma = false;
if (spicfg)
can_dma = spicfg->io_type == SPI_IO_TYPE_DMA;
can_dma = (spicfg->io_type == SPI_IO_TYPE_DMA) &&
(xfer->len >= DMA_MIN_BYTES);
return can_dma;
}
@ -620,10 +623,9 @@ static int davinci_spi_bufs(struct spi_device *spi, struct spi_transfer *t)
reinit_completion(&dspi->done);
if (spicfg->io_type == SPI_IO_TYPE_INTR)
set_io_bits(dspi->base + SPIINT, SPIINT_MASKINT);
if (spicfg->io_type != SPI_IO_TYPE_DMA) {
if (!davinci_spi_can_dma(spi->master, spi, t)) {
if (spicfg->io_type != SPI_IO_TYPE_POLL)
set_io_bits(dspi->base + SPIINT, SPIINT_MASKINT);
/* start the transfer */
dspi->wcount--;
tx_data = dspi->get_tx(dspi);
@ -698,7 +700,7 @@ static int davinci_spi_bufs(struct spi_device *spi, struct spi_transfer *t)
}
clear_io_bits(dspi->base + SPIINT, SPIINT_MASKALL);
if (spicfg->io_type == SPI_IO_TYPE_DMA)
if (davinci_spi_can_dma(spi->master, spi, t))
clear_io_bits(dspi->base + SPIINT, SPIINT_DMA_REQ_EN);
clear_io_bits(dspi->base + SPIGCR1, SPIGCR1_SPIENA_MASK);